Flow meter with measuring channel

ABSTRACT

Disclosed is a flow meter with at least two measuring sensors, preferably ultrasonic sensors, spaced apart from each other, wherein the coupling of the measuring signals into and out of a fluid is performed via a coupling element According to the disclosure, the measuring channel is formed with an approximately oval or trapezoid cross-section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of, and claims priority to, PatentCooperation Treaty Application No. PCT/EP2017/067765, filed on Jul. 13,2017, which application claims priority to German Application No. DE 102016 112 882.1, filed on Jul. 13, 2016, which applications are herebyincorporated herein by reference in their entireties.

DESCRIPTION

The disclosure relates to a flow meter described below.

Such flow meters can, for example, have two ultrasonic transducers,which are inserted as so-called “clip-on-solutions” at a distance fromeach other in a pipe section of the pipe, wherein both transducers actas emitter and receiver. The measuring signals are coupled obliquelythrough the pipe-section wall into the fluid.

The flow speed can then be determined from the runtime of the measuringsignals from the emitter to the receiver in a manner known per se. Suchflow meters are described, for example, in the printed publications WO2004/036151 A1 and DE 10 2005 057 888.

The disadvantage of clip-on-flow meters is that the measuring signalspenetrate the wall of the measuring channel, so that different measuringsignals are obtained for different materials of which the measuringchannel can be made, so that the influence of the material must be takeninto account in the measuring signal evaluation.

Furthermore, solutions are known having a measuring insert in which theultrasonic transducers are accommodated. This measuring insert isinserted into a recess of a pipe section/measuring channel, wherein theactual measuring channel can also be a part of this measuring insert.

Such a solution is disclosed, for example, in DE 101 20 355 A1, whereinthe two ultrasonic transducers are arranged in the flow direction at adistance from each other and on opposite sides of the measuring channel.

In EP 2 306 160 A1, a flow meter/flow counter is disclosed, in which themeasuring insert accommodates the ultrasonic transducer and also formsthe actual measuring channel. This measuring insert is attached to atangential flange of a pipe section of a housing of the flow meter. Aprofile body forming the measuring channel immerses into a recess of thepipe section surrounded by the flange, which influences the streamingwithin the measurement area, and on which reflectors for the measuringsignals are additionally provided. In this solution, the two ultrasonictransducers are arranged in a pot-shaped housing part of the measuringinsert, which is closed towards the streaming and is immersed in it.

A similar solution is shown in EP 2 386 836 B1. In this example, themeasuring insert carries two ultrasonic transducers arranged in thestreaming direction offset to each other, which are also accommodated ina pot-shaped housing part and which project into the measuring channelthrough an opening, which is surrounded by a flange, of a pipe sectionof a housing. The stream guidance within the measuring channel isdetermined by a housing insert which can be inserted from the front sideof the housing and which also carries reflectors for the ultrasonicsignals, so that the ultrasound is emitted by one of the ultrasonictransducers and reflected via the reflectors to the other ultrasonictransducer, which is located downstream, for example. Of course, thesignal can also be guided in the reverse direction.

In the published publication EP 0 890 826 B1, a flow meter is described,in which a measuring insert is also attached to a tangential flange inthe area of a pipe section of a housing. The measuring insert carriestwo ultrasonic transducers which are inserted into the recesses of abottom of a housing part and are sealed there by means of a respectiveseal. The whole measuring insert is then sealed against the flange withanother circumferential seal, which encompasses both ultrasonictransducers. In this example, the measuring channel is also formed bythe measuring insert, which is inserted into the pipe section of thehousing through the recess encompassed by the flange. This measuringchannel is rectangular.

In all solutions described above, the reflectors are formeddiametrically with respect to the ultrasonic transducers, so that atleast two reflectors must be provided in order to guide the ultrasonicsignals.

In the latter flow meter, the two ultrasonic transducers are eacharranged in a sensor housing, hereafter called coupling element, andproject radially into the measuring channel so that the fluid flowsaround them.

A disadvantage of such solutions is that the streaming in the area ofthe measuring channel, in particular in the area of sensors, breaks offor becomes swirled so that measurement errors occur, in particular forsmall nominal widths.

In view of this, the disclosure is based on the object of creating aflow meter/flow counter with improved measuring accuracy.

This object is solved by a flow meter as described below.

According to the disclosure, the flow meter has a measuring channelwhich can be attached to a pipe through which a fluid flows and on whicha measuring unit is held which has at least two measuring sensors,preferably ultrasonic transducers, which are spaced apart from eachother and which are immersed in at least one recess of the measuringchannel. The coupling and decoupling of the measuring signals into andout of the fluid takes place via a common or a respective couplingelement, which accommodates the measuring sensor(s).

According to the disclosure, the measuring channel is designed with across-section profile that has a larger nominal width in theemitter/receiver direction of the sensors than transverse to it.According to the disclosure, this is formed in that the measuringchannel has an oval shape. Alternatively, the measuring channel may alsohave a trapezoid shape.

Due to this even, rounded cross-section profile, the streaming can bemade more even for an optimal, enlarged signal path as compared to knownsolutions with a rectangular profile or a round profile, so that themeasuring accuracy is improved as compared to conventional solutions.

The entire cross-section is preferably designed to be slightly smallerthan the inlet and outlet cross-section of the flow meter, so that thefluid stream is accelerated in the area of the measuring channel. Byincreasing the dimensions in the emitter and receiver direction, thesignal path and thus the runtime of the signal are also increasedcompared to a round cross-section.

In a particularly preferred example, the measuring channel isapproximately oval in shape, i.e. the measuring channel is not limitedby straight walls in the direction of its high axis, but by slightlyconcavely curved side walls—this contributes to further even out thefluid stream.

In a particularly preferred example, the side walls running in thedirection of the high axis (approximately in emitter and receiverdirection of the ultrasonic signals) are curved and form theaforementioned oval shape with approximately flat or slightly curvedtransverse walls running approximately in the direction of thetransverse axis. Surprisingly, it turned out that such an oval geometryguarantees optimal streaming and an accompanying maximum signal quality.

In an alternative solution, instead of the oval shape, a roughlytrapezoidal cross-section can be formed, wherein a transverse wallcomparatively wide in the transverse direction is formed on the sensorside and a transverse wall with a significantly smaller width or arounding is formed on the reflector side.

Advantageously, the coupling element is inserted flush into acircumferential wall of the measuring channel. This means that neitherthe coupling element nor the actual measuring sensor or another housingpart project into the measuring channel, so that the measuring accuracyis significantly increased as compared to conventional solutions due tothe more even streaming.

According to an example, the coupling elements are inserted flush intoone of the transverse walls of the measuring channel.

The coupling of the signals is optimal if the coupling element has acoupling wedge that is inclined obliquely to the measuring channel axisand on which the ultrasonic transducer rests.

Sealing is particularly simple if this coupling element is sealed bymeans of a seal in the measuring channel.

Advantageously, the ratio of the width of the measuring channel in thevertex of the curvature of the side wall to the width of the transversewalls in the transverse direction can be >1.2, preferably approx. 1.3 to1.6. Alternatively or additionally, the ratio of the height extension ofthe side wall to the width of the transverse wall can be >1.5,preferably approx. 1.5 to 2.

The fluid stream can be further evened out if, for example for smallnominal widths, the coupling element extends as far as into the sidewall. Also in this area, the coupling element is flush with the sidewall, so that there are no projecting components that interfere withstreaming.

In an example, the coupling element or several coupling elements areattached to a measuring housing which accommodates the controlelectronics, further sensors, a battery pack, communication modulesand/or a power supply. The battery pack can preferably be designed to bereplaceable.

In one example, the measuring housing is designed with a bottom in whichthe coupling element(s) with the ultrasonic transducers are inserteddirectly or by means of a sensor accommodation.

The construction of the housing of the flow meter is further simplifiedif the measuring channel has a flange that encompasses at least onerecess into which at least one coupling element is immersed and to whicha system adapter of the measuring housing is attached.

According to a further development, a reflector device is arranged onthe transverse wall remote from the ultrasonic transducers, which ispreferably inserted flush into a pocket of the transverse wall.

By the flush insertion of the reflector/mirror and/or of thesensors/coupling element into the measuring channel, turbulences andstreaming stalls are prevented in the area of these components as wellas an associated dirt deposition and the resulting signal falsification.

The construction can be further simplified if the pipe section forms themeasuring channel. This requires that the pipe section is constructedaccording to the above-defined specifications (oval shape).Alternatively, the measuring channel can also be inserted into the pipesection.

In another example, the flow meter has a housing that has two inlet andoutlet mounting flanges between which the pipe section and/or themeasuring channel extends, the flow cross-section in the lead-in area orrespectively the lead-out area of the mounting flanges being smallerthan in the measuring channel.

The signal quality can be further improved if the coupling element ismade of PEEK, PSU or PEI.

In a further preferred solution, a double sensor is accommodated in acoupling element so that two approximately parallel signal paths areformed.

In order to further improve the measuring accuracy, a reference path canbe formed in each coupling element, which is determined by the geometryof the coupling element and its material.

In such a coupling element, a temperature sensor or another sensor canbe accommodated which, for example, detects heating of the fluid or thecoupling element during the measurement and can make a correspondingsignal correction.

The Applicant reserves the right to base independent patent claims onthe double sensor or the geometry of the coupling element with areference path and/or with an additional sensor or the type of sealingof the measuring insert, which can be made the subject matter ofdivisional applications or the like.

According to an example, the coupling elements are combined to form ameasuring bar.

This measuring bar can also be formed with a reference path, which forexample enables a zero drift correction.

The influence of air bubbles and sedimentations can be reduced bytilting or horizontal positioning of the profile cross-section—thissolution can also be used as subject matter of an independent patentrequest.

Examples of the disclosure are explained in more detail below usingschematic drawings. These show:

FIG. 1 shows a first example of a flow meter executed with a measuringinsert;

FIGS. 2a, 2b show further partial drawings of a flow meter according toFIG. 1;

FIGS. 3a, 3b, 3c, 3d show views of a further example of a flow meteraccording to the disclosure;

FIGS. 4a, 4b, 4c, 4d show views of a third example of a flow meteraccording to the disclosure;

FIGS. 5a, 5b, 5c, 5d, 5e, 5f show a further example of a flow meter,wherein a measuring channel is formed by a measuring insert;

FIGS. 6a, 6b show a partial drawing of a measuring bar/coupling elementof the example according to FIGS. 5a, 5b, 5c , 5 d;

FIGS. 7a, 7b show two further examples of a flow meter according to thedisclosure;

FIGS. 8a, 8b, 8c, 8d, 8e show views of a housing of the flow meteraccording to FIGS. 7a , 7 b;

FIG. 9 shows a further drawing of the example according to FIG. 7 a;

FIG. 10 shows an exploded view of a measuring insert of the exampleaccording to FIG. 9, 7 a;

FIG. 11 shows a further view of the measuring insert according to FIG.10 with a detail drawing of the measuring bar according to FIGS. 6a , 6b;

FIG. 12 shows views of a battery pack of a flow meter according to thedisclosure;

FIG. 13 shows an exploded view of the battery pack according to FIG. 12;

FIG. 14 shows a schematic diagram of a further example of a flow meteraccording to the disclosure with measurement attachment;

FIGS. 15a, 15b and 15c show views of a further example of a flow meterwith a measurement attachment;

FIG. 15d shows a variation of the example according to FIGS. 15a, 15b ,15 c;

FIGS. 16a, 16b, 16c show main component groups of a further example of aflow meter according to the disclosure with a measurement attachment;

FIGS. 17a, 17b, 17c show variations of the example according to FIGS.16a, 16b, 16c with external modules;

FIGS. 18a, 18b, and 19a, 19b show variations of a housing of a flowmeter according to FIGS. 16a, 16b, 16c, 17a, 17b , 17 c;

FIG. 20 shows a schematic diagram for explaining the structure of anultrasonic transducer according to the disclosure;

FIGS. 21a, 21b, 21c, 21d show an example of a measuring insert for ahousing according to FIGS. 19a , 19 b;

FIGS. 22a, 22b, 22c, 22d show drawings of a measurement attachment for ahousing according to FIGS. 18a , 18 b;

FIG. 23 shows a variation of the example of a measurement attachmentaccording to FIGS. 22a, 22b, 22c , 22 d;

FIG. 24 shows a schematic diagram on the structure of a double sensor;

FIGS. 25a, 25b show schematic diagrams for explaining the course of thesignal paths of a double sensor;

FIGS. 26a, 26b, 26c show an example of a flow meter with an additionalsensor, e.g. a pressure sensor;

FIGS. 27a, 27b show drawings of a flow meter with an external sensormodule;

FIG. 28 shows a variation of a double sensor with an additional sensor,e.g. a temperature sensor;

FIGS. 29a, 29b, 29c, 29d show drawings of three examples for referencepaths for zero drift correction integrated into a coupling element;

FIGS. 30a, 30b show drawings of a further example of a flow meter withdouble sensors;

FIGS. 31a, 31b show drawings of a flow meter in which four singlesensors are used instead of the double sensors, and

FIGS. 32a, 32b show a comparison illustration of the flow meters ofFIGS. 30a, 30b, 31a , 31 b.

FIG. 1 shows a first example of a flow meter 1 executed with a measuringinsert 2. The flow meter 1 has a housing 4, which has two mountingflanges 5, 6, between which a pipe section 8 extends. This housing 4 isinserted into an installed pipe through which the medium/fluid flowswhose flow is to be measured.

The pipe section 8 has an approximately tangentially arranged flange 10,which encompasses a recess 12. The actual measuring insert 2 has ameasuring channel 14, to which a sensor system as described below isassigned.

The control electronics and power supply and other components of theflow meter 1 required for signal processing are accommodated in ameasuring housing 16. Furthermore, a display for the measured flow whichis not visible in FIG. 1 is provided on this housing. The measuringchannel 14 is inserted through the recess 12 of the housing 4 into thecross-section of the pipe section 8 and the measuring housing 16 is thenfixed at the flange 10.

FIG. 2a ) shows an exploded view of a part of the measuring insert ofthe flow meter according to FIG. 1, and FIG. 2b ) shows the flow meterin the mounted state.

In the drawing according to FIG. 2a ), the housing 4 is shown with thepipe section 8, which lies between the two mounting flanges 5, 6.Tangentially to the pipe section 8 (in FIG. 2a ) pointing upwards) theflange 10 is formed, which encompasses the recess 12, through which themeasuring insert 2, in particular the measuring channel 14, can beinserted into an interior space 20 of the pipe section 8.

For stream guidance in the inlet and outlet area, a lead-in and alead-out body 22, 24 are inserted in the pipe section 8 or respectivelyin the mounting flange on the inlet and outlet side, wherein in theassembled state, these bodies establish a substantially fluid-tightconnection to the measuring channel 14.

As explained in more detail below, this measuring channel 14 does nothave a circular or rectangular cross-section, but is designed in an ovalshape to reduce streaming stalls and turbulences. In the example shown,the measuring channel 14 is attached to a system adapter 26 of themeasuring insert 2 or the measuring housing 16. This system adapter 26is also provided with two ultrasonic transducers—hereinafter referred toas sensors 28, 30—which are arranged on coupling elements 32, 34, viawhich the ultrasonic signals are coupled into or out of the fluid.

FIG. 2a ) at the top shows a housing bottom 36 of the measuring housing16 mounted on the system adapter 26.

FIGS. 3a ) and 3 b) show the measuring channel 14, which in turn isattached to the system adapter 26. As indicated in FIG. 3a ), themeasuring channel 14 is surrounded in the connection area to the systemadapter 26 by a circumferential sealing ring 38, which rests on theflange 10 in the mounted state. The system adapter 26 in turn is coveredby the housing bottom 36.

This drawing shows that the measuring channel 14 made of plastic, forexample, does not have a circular but an oval flow cross-section with ahigh axis h and a transverse axis q. The high axis h is longer than thetransverse axis q. In the example shown, the ratio of the dimensions ish:q>1.2, preferably about 1.5. The ratio of the length of the high axish to the width b shown in FIG. 3a ) is (a:b)>1.5, preferably about 2.

The width b indicates the width of transverse walls 40, 42, which aredesigned as flat surfaces or slightly concavely curved walls. In thedirection of the high axis h, side walls 44, 46 extend, which togetherwith the transverse walls 40, 42 define an approximately ovalcross-section of the measuring channel 14. This ovalized, roundedcross-section form reduces streaming stalls and turbulences as comparedto the conventional right-angled or circular channel cross-sections,whereby the signal propagation and the signal path are increased by thelarge height extension h and the streaming speed can be significantlyincreased as compared to the inlet area and outlet area by thecomparatively small width q, b in the transverse direction. It is aprerequisite that the lead-in body 22 and the lead-out body 24 have across-section that is smaller than the cross-section of the measuringchannel through which the current flows, so that a correspondingincrease in velocity occurs.

FIG. 3c ) shows the arrangement according to FIG. 3a ) in athree-dimensional representation in a slightly different view. Asmentioned, the measuring channel 14 with the oval measuring channelcross-section is made of plastic and is surrounded by the sealing ring38 attached to the system adapter 26. In the system adapter 26, the twocoupling elements 32, 34 are arranged, of which only the couplingelement 32 is visible in the drawing according to FIG. 3c ). In thisdrawing, it can be seen that the coupling element 32 is inserted flushinto the flat or slightly curved transverse wall 42 on the sensor side,so that the measuring channel 14, or more precisely its circumferentialwall, is largely smooth with rounded transitions.

FIG. 3d ) shows a plan view of the arrangement according to FIG. 3c ),wherein the lead-in body 22 and the lead-out body 24 are attached to themeasuring channel 14. According to this drawing, the two couplingelements 32, 34 protrude slightly upwards beyond the large surface ofthe system adapter 26 visible in FIG. 3 towards the housing floor 36which is not shown. As will be described in more detail below, eachcoupling element 32, 34 has a coupling wedge 48, 50 to which—as will beexplained in more detail below—the sensor is attached. The wedge angleof the coupling wedge 48, 50 is selected such that the ultrasonicsignals generated by the sensor 28, 30 are coupled obliquely into themeasuring channel 14.

As shown in FIGS. 3a ), 3 b), the measuring channel 14 or the streamcross-section provided in it can be aligned in such a way that its highaxis h is set obliquely to the direction of gravity. In this way, aninterference of the measuring signals due to sedimentations, air bubblesor the like is prevented. This inclination is possible in all examplesdescribed. As mentioned at the beginning, a horizontal arrangement isalso possible, whereby the high axis of the oval profile is thenarranged transversely to the direction of gravity.

FIG. 4 shows a variation in which the flow meter 1 is executed accordingto the “measurement attachment” concept. The two coupling elements 32,34 are inserted directly into the transverse wall 42. The measuringchannel 14 in turn flows via the lead-in and lead-out bodies 22, 24 intothe two external mounting flanges 5, 6. In this example, the measuringchannel 14 is thus formed directly by the pipe section 8, whereas in theexample according to FIGS. 1 to 3, the measuring channel 14 is insertedinto the pipe section 8. The ovalized cross-section of the measuringchannel 14 is also provided for the example shown in FIG. 4, whose highaxis is set obliquely to the direction of gravity for the exampleshown—this is particularly clearly shown in FIGS. 4b ), 4 c) and 4 d).According to FIG. 4a ), the two coupling elements 32, 34 are—asexplained above—inserted into corresponding recesses of pipe sections 8and each have a coupling wedge 48, 50 on which the respective sensor 28,30 is supported. These sensors can, for example, be formed by apiezoceramic, which is contacted via electrodes with the controlaccommodated in the measuring housing 16.

The angle of inclination of the coupling wedge 48, 50 is formed in sucha way that the signals coupled into or respectively out of the measuringchannel 14 by the two sensors are inclined approximately V-shaped toeach other. The signal guidance is not limited to such a V-shape. Forexample, the signal path can also be W-shaped, whereby the measurementsignal is then redirected from a first, opposite reflector back toanother reflector, which is arranged between the two sensors. The signalis then directed from this reflector in the direction of a thirdreflector, which in turn is arranged on the opposite side and via whichthe measurement signal is reflected to the other sensor. The latterreflector is arranged in the same way as the first reflector. Thecentral reflector on the sensor side can then be located at themeasuring channel or at the measurement attachment/measuring insert.Sealing of the coupling elements 32, 34 in the measuring channel 14 iscarried out via sealing rings which are not shown.

In the drawing according to FIG. 4b ), it is again clearly visible thatthe fluid-side coupling surfaces of the two coupling elements 32, 34 areinserted flush into the corresponding transverse wall 42, so that themeasuring channel 14 is surrounded by smooth circumferential walls.

FIG. 4c ) shows the measuring channel in a view from above, so that thetransverse wall 40 opposite the coupling elements 32, 34 is visible. Inthis plane or slightly rounded transverse wall 40, a reflector 52 isinserted which lies at the vertex of the V formed by the two sensoraxes. The signal path extends, for example, from a sensor 28 via thecoupling element 48 into the cross-section of the measuring channel 14towards the reflector 52. The measurement signal is then reflected fromreflector 52 to the other sensor 30, whereby the reflected signal isguided via the associated coupling element 34 and coupling the wedge 50to sensor 30.

FIG. 5 shows a variation of an example with “measuring insert”. Thisdrawing (see FIG. a)) shows the housing 4 described above with the twomounting flanges 5, 6, between which the pipe section 8 with the flange10 extends. The measuring channel 14 shown in FIG. 5d ) is inserted intothe recess 12 of the housing 4 surrounded by the flange 10. Thischannel, in turn, has a pocket-shaped accommodation 56 in which ameasuring bar 54 (FIG. 5b ) is inserted. This one-piece measuring bar 54replaces the aforementioned structure with two coupling elements and theassociated sensors. As shown in FIGS. 5d ) and 5 b) in particular, themeasuring channel 14 has a console 57 encompassing the accommodation 56with which it is attached to the system adapter 26.

In the example shown in FIG. 5e ), the system adapter 26 has a controlhousing frame 58, which forms part of the measuring housing 16 and inwhich an electronic module 60 shown in FIG. 5c ) is inserted, whichcontains all electronic components for power supply and signalprocessing. This electronic module 60 is connected to the sensors 28, 30via a connector 62 arranged on the measuring bar 54.

FIG. 5f ) shows the lead-in body 22, which is attached to the measuringchannel 14 in a substantially fluid-tight manner. The lead-out body 24has a corresponding structure. As can be seen from this drawing, the endsection on the measuring-channel side of the lead-in body 22 is adaptedto the oval profile of the measuring channel 14 with regard to thecross-section profile. As a result, streaming is already acceleratedwithin the lead-in body 22, since the cross-section tapers from thecircular input cross-section to the oval measurement cross-section.

FIGS. 6a ), 6 b) show detail drawings of the measuring bar 54 insertedinto the accommodation 56. It is made of plastic, e.g. PSU, PEEK, PEI oranother suitable material and is inserted fittingly into theaccommodation 56 of the measuring channel or more precisely into theconsole 57. The two sensors 28, 30, which are designed as piezoelements/piezoceramics, are attached to coupling wedges 48, 50, whichare integrally formed on the measuring bar 54. As can be seen inparticular from FIG. 6b ), the measuring bar 54 is pot-shaped. In thespace surrounded by the measuring bar 54, a printed circuit board 64 isarranged, which is connected to the connector 62 on the one hand and tothe two sensors 28, 30 on the other hand for power supply and signaltransmission. As can be seen in the drawing according to FIG. 6a ),connector 62 is sealed by a seal 66 in the control housing. The spacesurrounded by the measuring bar 54 is then filled with a castingcompound 68, so that the sensors 28, 30, the printed circuit board 64,the corresponding contacts, etc. are embedded and fixed in a fluid-tightmanner.

As shown in FIG. 6b ), a reference path 70 is formed in the measuringbar 54 between the two coupling wedges 48, 50 inclined towards eachother. The signal emitted by one sensor 28 can in principle move alongtwo signal paths to the respective other sensor 30. One signal path runsalong the reference path 70 shown in FIG. 6b ) through the measuring bar54 directly to the adjacent sensor 30. The other signal path 72 runsalong a comparatively short path in the measuring bar 54 and is thencoupled into the medium via this path. This signal path 72 continues tothe reflector 52 (not shown in FIG. 6) and from there towards the othersensor 30, wherein the signal from the fluid is coupled into themeasuring bar 54 and then hits the sensor 30 along a relatively shortpath through the measuring bar 54.

The reference path 70 provides the measuring electronics with areference signal that is independent of the flow of the fluid and cantherefore be used for zero drift correction.

FIGS. 7 to 11 explain further variations of the example according toFIGS. 5, 6. FIG. 7 shows two concrete examples of flow meters 1, whichare executed according to the principle “measurement attachment”. FIG.7a ) shows a flow meter 1 with the housing 4, to which the measuringhousing 16 with the control electronics, the counter and a digitaldisplay 74 shown in FIG. 7a ) is attached. FIG. 7b ) shows a variationin which communication modules 76 are additionally attached to themeasuring housing 16, which can be used, for example, to establish awireless signal transmission to a computer, a mobile readout station, aconnection to sensors or the like.

FIGS. 8a ) to 8 e) show the basic structure of the housing 4. Since thebasic structure of the housing 4 largely corresponds to that of thehousings described above, only a few design features are explained andfor the rest reference is made to the above explanations on the housingstructure.

FIG. 8a ) shows a three-dimensional drawing of the housing 4 with thetwo mounting flanges 5, 6 and the pipe section 8 in between, on whichthe tangentially running flange 10 is arranged. This encompasses recess12, into which the measuring insert, in the present case the measuringbar 54, is inserted in a fluid-tight manner.

FIG. 8b ) shows a longitudinal section through the housing 4 accordingto FIG. 8a ). It can be seen in this drawing that recess 12, whichpenetrates the flange 10, leads into the measuring channel 14 limited bythe pipe section 8.

Diametrically to recess 12, a pocket 78 is formed in measuring channel14, into which the reflector 52 described above is fittingly inserted,preferably pressed. FIG. 8c ) shows a section along the line A-A in FIG.8b ). In this drawing, the pocket 78, which leads into the transversewall 40 of the measuring channel 14 below, is clearly visible. Therecess 12 leads in a corresponding way into the transverse wall 42 atthe top. The reflector 52, which is not shown, is inserted into pocket78 through the recess 12 in this example.

Usually, the housing 4 is powder coated. However, the powder coating ispreferably not formed in the area of the pocket 78, so that the pressfit can be produced with high accuracy. The Applicant reserves the rightto base an independent claim on this press fit.

FIG. 8d ) shows a top view of the housing 4. This drawing clearly showsthe pocket 78 which can be reached through the recess 12. Also clearlyvisible is the H-shaped sealing surface of the flange 10 with thefastening recesses, via which the measuring housing 16 is fastened tothe flange 10.

FIG. 8e ) shows a side view of the measuring housing 4. A radiallyprotruding projection 80 in which the pocket 78 is formed is clearlyvisible. This projection 80 is diametrically opposed to the flange 10.

FIG. 9 shows a detail drawing of the measuring housing 16 of the exampleshown in FIG. 7a ). Accordingly, the housing has the already describedsystem adapter 26, which is formed in one piece with the control housingframe 58, which in turn accommodates the electronic module 60 and thedigital display 74. The measuring housing 16 is closed off by a housingcover as seen by the viewer in FIG. 9.

As explained above, the measuring bar 54 is mounted on system adapter 26and designed to be flush with recess 12 of the housing 4 (see FIG. 8).

FIG. 10 again shows an exploded view of the measuring housing 16. Asexplained, this consists in principle of the system adapter 26 with thecontrol housing frame 58. The electronic module 60 is inserted into thecontrol housing frame 58 and with the measuring bar 54 contacted viaconnector 62. The electronic module 60 contains the digital display 74described above, the counter and the other components required forsignal processing and power supply. The digital display 74 is thencovered by a transparent pane 84 and fixed to the control housing frame58 via the housing cover 82.

The example explained on the basis of FIGS. 9 and 10 has an exchangablebattery pack 86 which can be inserted into the measuring housing 16. Forthis purpose, the control housing frame 58 is formed with a batterysupply opening 88, through which the battery pack 86 can be insertedinto a holder 90 of the electronic module 60. This holder 90 then hascorresponding contacts so that the electronic components are suppliedwith power via the battery pack 86.

FIG. 11 shows a view from below of the measuring housing 16 according toFIG. 9. In this drawing, the battery pack 86 is inserted into thecontrol housing frame 58 and thus also into the electronic module 60.The measuring bar 54 protrudes downwards from the system adapter 26.

FIG. 12 shows again two detailed views of the battery pack 86, which hasa lid 92 with two shells 94, 96 shown in FIG. 13, forming an enclosinghousing for the actual battery block 98. The contacts 100 for contactingthe electronic module 60 protrude from the front face of the housingremote from the lid 92.

FIG. 14 shows a variation of the examples described above in which themeasuring channel 14 formed by the pipe section 8 is not oval buttrapezoidal in the broadest sense. The measuring channel 14 has—similarto the examples described above—two side walls 44, 46, which extendbetween a sensor-side transverse wall 42 and a lower transverse wall 40.The two side walls 44, 46 are arranged approximately V-shaped to eachother, so that the width B of the transverse wall 42 is clearly largerthan the width b of the transverse wall 40. Due to this approximatelytrapezoidal geometry, a cross-sectional narrowing occurs in turn in thedirection of the transverse axis, while in the direction of the uprighthigh axis a signal path is created that is larger than a circularcross-section.

As shown in FIG. 14, the reflector 52 is inserted in the area of thenarrower transverse wall 40 lying below. The wider transverse wall 42 atthe top is designed with flange 10, to which a measurement attachment 2with two single or double sensors 28, 30 can be attached. The basicstructure of each of the measurement attachments or measuring insertsdescribed can be used.

In FIGS. 15a ) to 15 d) further examples of flow meters 1 are shown.FIGS. 15a ), 15 b) and 15 c) show different views of a flow meter 1 inwhich the sensor system is designed as a measurement attachment. As withthe examples described above, a measurement attachment 2 with ameasuring housing 16 is attached to the housing 4 with the two mountingflanges 5, 6, with one or more communication modules for signaltransmission attached to it.

FIG. 15d ) shows a variation with a digital display 74.

The examples shown in FIG. 15 are in principle made up of two maincomponents, the measuring housing 16 shown in FIG. 16a ) and the housing4 shown in FIG. 16b ). The measuring housing 16 is designed as ameasurement attachment and is attached to the flange 10 of the housing4. This assembly process is shown schematically in FIG. 16c ). Thisdrawing shows the two sensors 28, 30, which are inserted in theopenings/recesses of flange 10 explained in more detail below.

Depending on the case of application, other modules can be attached tothe measuring housing 16—as explained above—for example the L-shapedcommunication modules 76 explained above (see FIG. 17a )). Thisattaching is shown in FIG. 17b ). In the example shown, the measuringhousing 16 is designed with a swiveling cover 102, which can be openedto insert the communication modules 76 or other modules, so that theycan be inserted into corresponding slots and contacted with theelectronic module 60. After this insertion, the cover 102 is closed (seeFIG. 17c )) so that the communication modules 76 or othermodules/components are fixed in position and contacted if necessary.

On the basis of FIGS. 18 and 19, two basic possibilities of the designof the housing 4 are explained.

Both housing variations do not differ in the geometry of the measuringchannel 14, which is again designed as an oval profile. This ovalprofile is shown in the common side view (c)) with the two variations(FIGS. 18, 19).

In the example of the housing 4 shown in FIG. 18, the flange 10 isdesigned with a single recess 12 into which the measuring insert withthe sensor system is inserted. As shown in FIG. 18a ), the reflector 52is mounted through the recess 12, whereby the reflector 52 is theninserted—similar to the example in FIG. 8—into a pocket 78 of the pipesection 8. This pocket 78 can again be formed in a projection 80.

FIG. 19 shows a variation in which not a single recess but a separaterecess 12 a, 12 b is provided for each sensor 28, 30, into each of whicha sensor 28, 30 is inserted, the basic structure of which is explainedusing FIG. 20. With these relatively small recesses 12 a, 12 b, it isdifficult to mount the reflector 52 through these recesses. For thisreason, it is preferred with such an example to design the projection 80with the pocket 78 open towards the outside, so that the reflector 52can be inserted into the pocket 78 from the outside. Sealing is thencarried out using a sealing cap 104.

As with the examples described above, the measuring signals are coupledin and out via an upper, preferably flat or slightly curved transversewall 42, with the sensors inserted flush into the wall. The reflector 52is inserted in a corresponding manner into the opposite transverse wall40, which is spaced from the sensors.

FIG. 20 shows the basic structure of the sensors 18, 20 as it can beused with the examples described above. Each sensor 18, 20 is held in acoupling element 32, 34. As previously explained using the measuring bar54, each coupling element 32 has a coupling wedge 48 with the respectivesensor 18 at its inclined wedge surface.

Like the measuring bar 54, the coupling element 32 and the couplingwedge 48 are made of a suitable plastic such as PEEK, PSU or PEI. Ofcourse, other materials can also be used which fulfill the followingcriteria: the material should enable signal transmission with a stablesound velocity in the range from 2000 to 2400 m/s, the temperatureinfluence should be as small as possible or at least linear, thematerial should have a low coefficient of linear expansion, the materialshould have sufficiently good adhesive and casting properties and shouldalso have low water absorption or only a slight change in the relevantproperties due to water absorption. In addition, the material should besuitable for use in drinking water environments and be comparativelyinexpensive.

In the example shown, the coupling element 32 is approximatelypot-shaped, whereby an accommodation chamber 106 is filled with acasting compound or the like. A ring flange 108 is provided on the outercircumference of the coupling element 32, which in the assembled statestretches over an O-ring 110, so that the coupling element 32 can beinserted in a sealing manner into an accommodation in the housing 4 orin the measuring housing 16. The acoustic and mechanical coupling of thesensor 18 to the coupling wedge 48 is carried out via a grease, gel,silicone pad and/or adhesive. This layer is marked in FIG. 20 with thereference sign 112. The contact of the sensor, i.e. of the piezoceramicfor example, is made via two electrodes 114 a, 114 b, whereby the lowerelectrode 114 b, which is on the coupling wedge side, is led upwards onone side to the other electrode 114 a, so that contacting is simplifiedfrom above.

On the basis of FIG. 21, the structure of a measurement attachment 2 fora housing according to FIG. 19 is explained. As described above, thisexample of a housing 4 has two individual recesses 12 a, 12 b (see FIG.21d )), into each of which a sensor 28, 30 with the associated couplingelement 32, 34 is inserted in a sealing manner. As shown in FIG. 21d ),the two coupling elements 32, 34 with the sensors 28, 30 integratedtherein but not shown as well as the two O-rings 110 are insertedindividually into the respective recesses 12 a, 12 b and sealed there bymeans of the O-rings 110. The measuring housing 16 is then placed ontothe flange 10, whereby the sealing ring 38 is arranged between thesystem adapter 26 of the measuring housing 16 and the flange 10 andencompasses the two sensors 28, 30 with the coupling elements 32, 34, sothat the electronic module 60 is also sealed towards the fluid. Asshown, for example, in FIG. 20b ), the coupling element 32 ends in aflush manner with the transverse wall 42 of the measuring channel 14. Inthe example explained in FIG. 21, this transverse wall is basicallyformed by the flange 10 of the housing 4. For small nominal widths, itcan happen that the coupling element 32, 34 has a slightly largerdiameter than the width of the transverse wall 42, so that the edgeareas of the coupling element 32, 34 extend as far as into the sidewalls 44, 46. In such a geometry it can be advantageous if—as in theexample according to FIG. 21a ), 21 c), 21 d)—the areas of a couplingsurface 116 formed in the transition area to the side walls 44, 46 areformed with protrusions 118 a 118 b (see FIG. 21 c)) extending to theside walls 44, 46, whereby these protrusions 118 a, 118 b run flush intothe side walls 44, 46, so that the coupling elements 32, 34 are fittedaccurately, without overhang or dug-out in the circumferential walls ofthe measuring channel 14.

The position fixing of the coupling elements 32, 34 in the measuringhousing 16 in the example shown in FIG. 21 is carried out via fixingelements 120 (see FIG. 21c, 21a )), which on the one hand encompass thecoupling elements 32 or 34 and on the other hand are attached to thesystem adapter 26. As explained above, in this example the reflector 52is mounted from the outside, whereby it is inserted into the pocket 78of the housing 4, which is open towards the outside.

A disadvantage of the direct fixation of the sensors 28, 30 and couplingelements 32, 34 in housing 4 is that the latter has a comparativelycomplex structure and therefore places relatively high demands on theproduction, especially the casting.

In the example according to FIG. 22, a housing according to FIG. 18 isused, which is easy to produce and in which the sensor system isinserted into a single large recess 12 of the flange 10. In the exampleshown in FIG. 22, the measuring housing 16 has a plate-shaped sensoraccommodation 121, e.g. made of plastic, which is connected to thesystem adapter 26 on the one hand and has two recesses 122 a, 122 b (seeFIG. 22d ) on the other hand, into each of which a coupling element 32,34 is inserted in a sealing manner. This sealing is performed usingO-rings 110 again. As shown in FIG. 22b ) in particular, the couplingelements 32, 34 are flush with the surface of the sensor accommodation121 on the measuring channel side when mounted. This surface thus formspart of the transverse wall 42 of the measuring channel 14—for thisreason, this surface is also given the reference sign 42 in FIG. 22b ).When mounted, the sensor accommodation 121 immerses into the recess 12of the flange 10 and is sealed there by an additional ring-shaped seal148 which rests on a shoulder 150 of the flange 10. Also in thisexample, the coupling elements 32, 34 and also the sensor accommodation121 are formed with projections 118 projecting towards the side walls44, 46, which ensure a continuous transition to the respective adjacentside wall 44, 46. As mentioned above, these projections 118 are notrequired for larger nominal widths, as the coupling elements 32, 34 canthen be inserted with their full surface into the transverse wall 42.

The sensor accommodation 121 and the system adapter are sealed withrespect to the flange 10 by means of the circumferential sealing ring38. Accordingly, four seals (two O-rings 110, the sealing ring 38 andthe seal 148) are required for the solution according to FIG. 22.

The technical effort can be further reduced if—as shown in FIG. 23—thetwo coupling elements 32, 34 are inserted into a sensor plate 124 of themeasuring housing 16, which is either formed on the system adapter 26 orattached to it. This means that the function of the sensor accommodation121 explained in FIG. 22 is integrated in the measuring housing 16.

The sensor plate 124 has according to the drawing in FIG. 23d ),accommodations 122 a, 122 b, in which the two coupling elements 32, 34are inserted in a sealing manner. Sealing is achieved by means of theO-rings 110. The position of the coupling elements 32, 34 is then fixedby means of fixing elements 120, which hold the sensor system in themeasuring housing 16.

In this example, at least a part of the sensor-side transverse wall 42is formed by the sensor plate 124. For small nominal widths, the twoprojections 118 can again be formed on the coupling element 32, 34 andaligned to it on the sensor plate 124 (see FIGS. 23a ), 23 c)) so that acontinuous transition to the adjacent side wall 44, 46 is ensured. Themeasuring housing 16 with the sensor plate 124 is then again sealed bymeans of the circumferential sealing ring 38 (FIG. 23c )) with respectto the housing 4. For this purpose, the sensor plate 124 is immersed inthe recess 12 of the flange 10.

In the example shown in FIG. 21, only three seals (two O-rings 110 andthe sealing ring 38) are required.

Due to the comparatively large recess 12, the reflector 52 of thisexample can also be inserted through the recess 12 into the pocket 78 ofthe pipe section 8, whereby the reflector 52 is also inserted flush andaligned into the transverse wall 40 below.

In the examples described above, a single sensor 28, 30 is arranged ineach coupling element 32, 34. FIG. 24 shows an example in which twosensors 28 a, 28 b; 30 a, 30 b are arranged in each of the two couplingelements 32, 34. These sensors 28, 30 are connected to coupling wedges48, 50 of the respective coupling element 32, 34. The fixing in themeasuring housing 16 is again achieved by means of fastening means, forexample screws and/or fixing elements 120. As explained above, also morethan two sensors 28, 30 can each be integrated into one couplingelement. In the drawing according to FIG. 24, one of the two protrusions118 a can be seen, which enter flush into the side walls 44, 46. In thedrawing according to FIG. 24, also a circumferential ring groove 126 forthe accommodation of an O-ring 110 is visible.

Such a double sensor has the advantage that two parallel signal pathscan be formed, as shown in FIG. 25 for example. At the top, an exampleof a flow meter 1 with a comparatively small nominal diameter of DN50 isshown. The indicated measuring channel has, for example, an uppertransverse wall 42 in which the two double sensors, i.e. the twocoupling elements 32, 34 with the respective sensors 28 a, 28 b and 30a, 30 b, are inserted flush. The coupling elements 32, 34 run with theircoupling surfaces 116 flush to the transverse walls 42, whereby due tothe small nominal width in the transition area to the side walls 44, 46,the coupling elements 32, 34 are each designed with the mentionedprotrusions 118 a, 118 b, which run flush into the side walls 44, 46.

As explained at the beginning, such a double sensor is preferably usedfor lower nominal widths with a coupling element 32, 34 common to bothsensors 28, 30. For larger nominal widths, two parallel single sensorsare preferably used instead of a double sensor, so that four singlesensors are held at the measurement attachment/measuring insert insteadof two double sensors.

With such double sensors or single sensors arranged in pairs, themeasurement takes place along two parallel signal paths 128 a, 128 b,which run for small nominal widths (see FIG. 25a )) at a comparativelysmaller distance than for large nominal widths (see FIG. 25b )). Withsuch large nominal widths, the sensor-side transverse wall 42 is so widethat this width is larger than the diameter of the coupling elements 32,34, so that it is possible to dispense with the formation of theprotrusions 118 and thus the coupling surface 116 is flat or is formedaccording to the slight curvature of the transverse surface 42.

FIG. 26 shows a design variation in which, in addition to the twosensors 28, 30 with the associated coupling elements 32, 34, a furthersensor is provided, for example a pressure sensor 130. The example shownin FIG. 26 has the basic structure of the example according to FIG. 23,in which the two sensors are integrated into the measuring housing. Thetwo coupling elements 32, 34 according to FIG. 26d ) are inserted intothe accommodations 122 a, 122 b of the sensor plate 124 on the measuringinsert side. The pressure sensor 130 is located in the area between thetwo accommodations 122 a, 122 b or respectively the coupling elements32, 34 inserted therein. Contact is established via contacts 132, whichproject through the sensor plate 124 and the system adapter 26 into thespace surrounded by the control housing frame 58 and are contacted therewith the electronic module 60 (see FIGS. 26b ) and 26 d)).

The drawing according to FIG. 26c ) clearly shows the flush embedding ofthe coupling elements 32, 34 into the measuring channel 14. On the leftside, the two protrusions 118 are visible, which enter flush into theside walls 44, 46.

In the example described above, the pressure sensor 130 is thusintegrated into the control housing. FIG. 27 shows an example in which apressure sensor module 134 is attached to the side of the pipe section8, i.e. approximately in the middle of the side walls. Signaltransmission and power supply are then carried out via a flexible line(power/signal transmission chain) 136, which is connected to theelectronic module 60 or the battery pack 86 of the measuring housing 16.This connection of line 136 can be made in approximately the same way asit is provided for the communication modules (see FIG. 17b )).

FIG. 28 shows a variation of the double sensors according to FIG. 24.The basic structure corresponds to that of FIG. 24, so that explanationsin this regard are unnecessary. In addition to the two double sensors,in the example according to FIG. 28, temperature sensors 138 areaccommodated in the respective coupling elements 32, 34, by means ofwhich the temperature of the sensors 28, 30 and/or of the couplingelements 32, 34 can be detected and corresponding signal corrections canbe made in the event of a change in temperature. These temperaturesensors 138 can, for example, be inserted into suitable recesses/pocketsin the area of the coupling wedge of the 48.

FIG. 29 illustrates again the possibilities for the formation of areference path.

FIG. 29a ) shows the already described reference path 70 (P2) inmeasuring bar 54, which extends from one sensor 28 in a zigzag patternto the other sensor 30. The actual signal path 72 (P1) exits themeasuring bar 54 after a comparatively short distance, whereby thisoccurs via the coupling surface 116 which is flush with the measuringchannel 14.

FIG. 29b ) shows a possibility to form such a reference path P2 also ina coupling element 32. In this case, for example, a mirror 140 isarranged in the coupling element 32 in parallel to the sensor 28, whichis supported by the coupling wedge 48. The measuring signal is thenreflected via this mirror 140 and redirected back to the sensor 28,which then receives the transmitted signal again and thus makes acorrection possible. The measuring beam P1 enters the measuring channelin a manner known per se via the coupling surface 116.

In a double sensor according to FIG. 29c ), the coupling element 32 isdesigned in such a way that, for example, part of the signalstransmitted by the sensor 28 a are reflected in the coupling element 32and deflected to the sensor 28 b arranged in parallel, so that thissensor 28 b receives the signal of the sensor 28 a—a reference path P2is again formed, which extends between the two sensors 28 a, 28 b. Themajority of the signals are coupled into the measuring channel or thefluid flowing through it via the coupling element 32 and the couplingsurface 116 in a manner known per se. The drawing according to FIG. 29again indicates the protrusions 118 a, 118 b which are advantageous fora small nominal width.

In the examples described above, the oval cross-section of the measuringchannel 14 with its high axis is either arranged in the verticaldirection (i.e. in the direction of gravity) or obliquely to it. Inprinciple, this “high axis” can also be arranged horizontally, i.e.transversely to the vertical direction.

FIG. 30 shows a flow meter 1 with a double sensor, as explained in FIGS.24, 25, 28 and 29 c).

As shown in FIG. 30a ), housing 4 is in principle designed like in theexamples described above. Accordingly, the housing has a flange 10formed on the pipe section 8, on which the two recesses 12 a, 12 b forthe coupling elements 32, 34 (see FIG. 30b )) are formed. In contrast tothe examples described above, the end sections forming the couplingelements 32, 34 or respectively their coupling surface 116 andprojecting into the recesses 12 a, 12 b are formed approximatelyrectangular with rounded “corner areas”. Accordingly, the recesses 12 a,12 b are also rectangular with rounded transitions between the shorterand the longer peripheral edges. As the drawing in FIG. 30a ) furthershows, each recess 12 a, 12 b has a shoulder 142 on which the respectiveO-ring 110 of the sensor 28, 30 rests in a sealing manner when mounted.In the example shown, the two sensors 28, 30, designed as doublesensors, are inserted into the system adapter 26. This system adapter26, for example, is pot-shaped (see FIG. 32) with correspondingaccommodations 144 for the sensors 28, 30. After inserting these sensors28, 30 into the accommodation 144 of the system adapter 26, the interiorcan be filled with a casting compound so that the sensors 28, 30 arereliably accommodated in a sealing manner. The system adapter 26 thencarries the control housing frame 58 in the above-described manner,which accommodates the electronic module 60 and the like that is notshown.

In the example shown in FIG. 30, a system adapter 26 is thus assigned toboth sensors 28, 30. In principle, it is also possible to accommodateboth sensors 28, 30 in one system adapter each. The system adapter 26 isalso called sensor plate. Such a solution with double sensors is—asmentioned at the beginning—especially used for flow meters 1 with asmall nominal width.

For larger nominal widths, a solution as shown in FIG. 31 is preferred.In such an execution according to FIG. 31b ), instead of the two doublesensors, four single sensors 28 a, 28 b, 30 a, 30 b each with a couplingelement 32 a, 32 b, 34 a, 34 b are used, to which four recesses 12 a, 12b, 12 c, 12 d are accordingly assigned in the flange 10 of the housing4. The basic structure of this solution with four single sensorscorresponds to that of the example according to FIG. 30. However, theindividual sensors 28 a, 28 b, 30 a, 30 b are not rectangular in shapebut oval, i.e. with rounded vertex edges and somewhat longerlongitudinal edges, which together form an approximately oval couplingsurface 116. Accordingly, recesses 12 a, 12 b, 12 c, 12 d are alsooval-shaped. The O-rings 110 also lie on shoulders 142 of the respectiverecesses 12 a, 12 b, 12 c, 12 d in this example. Corresponding shouldersfor the seals are in principle realized with all examples describedabove.

For sealing between the flange 10 and the system adapter, a sealing ring38 is again provided which is not shown.

As in the examples described above, the single and double sensors shownare each inserted in coupling elements 32, 34, whereby the respectivepiezoceramics each rest on a coupling wedge 50 of the coupling element30, 32. Since these elements are already described in detail above,reference is made to this explanation to avoid repetitions in thisregard.

As explained above, for the larger nominal widths, the distance betweenthe adjacent single sensors 28 a, 28 b or 30 a, 30 b—as shown in FIG.25b ) can be larger than for the example according to FIG. 30, so thatthe signal paths run at a larger parallel distance. In the exampleshown, all four sensors 28 a, 28 b, 30 a, 30 b are again accommodated ina common system adapter 26 and preferably fixed in position by means ofa casting compound 146.

In FIG. 32, the two concepts are arranged side by side in a longitudinalsection. FIG. 32a ) shows the longitudinal section of the exampleaccording to FIG. 30. In this drawing the two coupling elements 32, 34can be seen, on whose wedge surfaces 48, 50, two sensors 28 orrespectively 30 (only respectively one visible in FIG. 32a )) arearranged. These are each inserted into recesses 12 a, 12 b and sealedthere by means of the O-rings 110. The coupling surfaces 116 run flushto the peripheral wall (transverse wall 42 and adjacent areas of theside walls 44, 46) of the measuring channel 14, which in this example isformed by the pipe section 8. Part of the flange 10 thus forms thetransverse wall 42. The opposite transverse wall 40 of this example isformed with the pocket 78 open towards the outside, into which thereflector 52 is pressed.

In this drawing the casting compound 146 can be seen with which the twocoupling elements 32, 34 with the sensors 28, 30 are fixed in positionin the pot-shaped system adapter 26.

FIG. 32b ) shows a corresponding section of the flow meter according toFIG. 31. According to the relevant explanations, the two couplingelements 32, 34 of this example executed with single sensors areconsiderably more compact than in the example according to FIG. 32a .Each of the coupling elements 32 is sealed in the respective recess 12a, 12 b, 12 c, 12 d by means of an O-ring 110. All coupling surfaces areflush with the transverse wall 42.

In the drawing according to FIG. 32b ), the reflector 52 was not shownfor the sake of simplicity. In principle, however, it is located at thesame position as the aforementioned reflector 52. This is indicated by adotted line.

In principle, the technical effort in terms of devices and assembly isgreater for the example according to FIG. 32b ) than for the exampledescribed above, since, for example, four recesses 12 a, 12 b, 12 c, 12d and four single sensors 28 a, 28 b, 30 a, 30 b/coupling elements 32 a,32 b, 34 a, 34 b and corresponding O-rings 110 have to be provided,whereas for the example according to FIG. 31a ) only two of theserespective components are present.

In the examples described in FIGS. 30, 31, 32, the transverse wall 42 isformed by part of the flange 10. However, as explained above, instead ofthe individual recesses 12 a, 12 b, 12 c, 12 d, a comparatively largerecess 12 can also be provided, into which a system adapter 26 or asensor plate is then immersed, in which the coupling elements 32, 34 arethen arranged flush, so that the system adapter forms a part of themeasuring channel and the transverse wall 42 of the oval profile. Suchan example is explained, for example, in FIG. 22 above. In thisvariation, the system adapter 26 has a sensor accommodation 121 (sensorplate 124) in which the sensors 28, 30 are inserted.

In a preferred solution, the system adapter 26 itself is designed as asensor accommodation, whereby in contrast to the examples according toFIGS. 30, 31, 32, the coupling elements 32, 34 are inserted flush intothe system adapter or the sensor accommodation 121/sensor plate 124(these are then practically integrated into the system adapter 26).

The Applicant reserves the right to base independent claims on each ofthese concepts (arrangement of the sensors/coupling elements in the pipesection or flush in a sensor accommodation/a sensor plate or flush inthe system adapter).

In the examples according to FIGS. 21, 22, 23, too, the single sensorsor respectively their coupling elements 32, 24 can be fixed in positionwith the respective system adapter 26 or respectively the sensor plate124/the sensor accommodation 121 by means of the casting compound 146.

Disclosed is a flow meter with at least two measuring sensors,preferably ultrasonic sensors, spaced apart from each other, wherein thecoupling of the measuring signals into and out of a fluid is performedvia a coupling element According to the disclosure, the measuringchannel is formed with an approximately oval or trapezoid cross-section.

LIST OF REFERENCE SIGNS

-   1 flow meter-   2 measuring insert/measurement attachment-   4 housing-   5 mounting flange-   6 mounting flange-   8 pipe section-   10 flange-   12 recess-   14 measuring channel-   16 measuring housing-   20 interior-   22 lead-in body-   24 lead-out body-   26 system adapter-   28 sensor-   30 sensor-   32 coupling element-   34 coupling element-   36 housing bottom-   38 seal ring-   40 transverse wall-   42 transverse wall-   44 side wall-   46 side wall-   48 coupling wedge-   50 coupling wedge-   52 reflector-   54 measuring bar-   56 accommodation-   57 console-   58 control housing frame-   60 electronic module-   62 connector-   64 printed circuit board-   66 seal-   68 casting compound-   70 reference path-   72 signal path-   74 digital display-   76 communication module-   78 pocket-   80 projection-   82 housing cover-   84 pane-   86 battery pack-   88 battery supply opening-   90 holder-   92 lid-   94 shell-   96 shell-   98 battery block-   100 contacts-   102 cover-   104 sealing cap-   106 accommodation chamber-   108 ring flange-   110 O-ring-   112 adhesive, grease, gel-   114 electrode-   116 coupling surface-   118 projection-   120 fixing element-   121 sensor accommodation-   122 accommodation-   124 sensor plate-   126 ring groove-   128 signal path-   130 pressure sensor-   132 contact-   134 pressure sensor module-   136 flexible line-   138 temperature sensor-   140 mirror-   142 shoulder-   144 accommodation-   146 casting compound-   148 seal-   150 shoulder for seal

1.-17. (canceled)
 18. A flow meter having a measuring channel configuredto be attached to a pipe, through which measuring channel a fluid flowsand on which measuring channel a measuring unit is held, the measuringunit including at least two sensors, the at least two sensors spacedapart from each other and immersed in at least one recess of themeasuring channel, wherein a coupling of measuring signals into or outof the fluid is performed via a measuring bar or via a respectivecoupling element which accommodates at least one of the at least twosensors, wherein the measuring channel has a cross-section which hasapproximately in an emitter/receiver direction of the at least twosensors a larger clear width than transverse to it, and further whereinthe measuring channel has approximately an oval shape or is tapered in atrapezoidal form in a region opposite the at least two sensors, whereinside walls extending in a direction of a high axis are curved out andform the oval shape with transverse walls which are approximately flator slightly curved out and extend approximately in the direction of atransverse axis, wherein in one of the transverse walls remote from theat least two sensors a reflector is arranged which is inserted flush ina pocket of the transverse wall.
 19. The flow meter according to claim18, wherein the measuring bar or the coupling elements are insertedflush into one of the transverse walls.
 20. The flow meter according toclaim 19, wherein a ratio of a width of the measuring channel at avertex of curvatures to a width of the transverse walls is greater than1.2, and wherein a ratio of a height extension of the side walls to thewidth of the transverse walls is greater than 1.5.
 21. The flow meteraccording to claim 19, wherein each coupling element extends as far asinto the side walls.
 22. The flow meter according claim 18, wherein themeasuring bar or the coupling elements are attached to a measuringhousing which accommodates control electronics, further sensors, abattery pack, communication modules and/or a power supply.
 23. The flowmeter according to patent claim 22, wherein the coupling elements or themeasuring bar are directly attached in the measuring housing or attachedto the measuring housing by a sensor accommodation or a system adapter.24. The flow meter according to claim 22, wherein the measuring channelhas a flange which encompasses the recess and to which a system adapterwhich indirectly or directly carries the at least two sensors or asensor accommodation of the measuring housing is fastened, such thatcoupling surfaces of the coupling elements extend flush with aperipheral wall of the measuring channel.
 25. The flow meter accordingto claim 18, wherein at least one of the coupling elements or themeasuring bar has a coupling wedge which is inclined with respect to ameasuring channel axis and on which at least one sensor of the at leasttwo sensors rests.
 26. The flow meter according to claim 18, wherein atleast one of the coupling elements is sealed in the measuring channel bymeans of a seal.
 27. The flow meter according to claim 18, wherein themeasuring channel is at least in sections inserted into a pipe sectionor a pipe section itself forms the measuring channel.
 28. The flow meteraccording to claim 27 having a housing comprising two mounting flangesbetween which the pipe section and/or the measuring channel extends,wherein the cross-section in an inlet area or respectively outlet areaof the mounting flanges is larger than in the measuring channel.
 29. Theflow meter according to claim 18, wherein at least one of the couplingelements is made of PEEK, PSU or PEI or another suitable plasticmaterial.
 30. Flow meter according to claim 18, wherein in at least onecoupling element at least two sensors are accommodated.
 31. The flowmeter according to claim 18, wherein within at least one couplingelement or the measuring bar a reference path is formed.
 32. The flowmeter according to claim 18, wherein in at least one of the couplingelements or in the measuring bar or at a measuring housing, atemperature sensor or a pressure sensor or another sensor isaccommodated.
 33. The flow meter according to claim 18, wherein the atleast two sensors are ultrasonic sensors.